A technique for cutting metal which has been used for some time, is that of imposing a low voltage, high current electric source between the work to be cut, and a carbon electrode. An electric arc is formed between the electrode and the workpiece, which creates an area of high heat intensity, which melts a localized area of the workpiece. To remove the molten metal formed in the localized area, an air stream is directed to blow it away.
In order to effectively accomplish cutting of metal using this technique, a holder is required to perform plural functions, of holding the carbon arc electrode in a way so that the extension of the electrode from the holder can be easily adjusted, plus providing a means of maintaining low resistance electrical connection with the electrode, and at the same time providing a means of directing an air stream along the electrode to blow away molten metal formed in the cutting process.
One principal problem with the prior art types of holders is that it is necessary to make good electrical contact between the holder and the electrode, while at the same time providing an easy means for adjusting the length of the electrode relative to the holder. The arc formed by the electrode with the molten metal gradually eats away the carbon electrode, so that it must be periodically extended relative to the holder. For these reasons, a common means of using carbon arc electrodes is to utilize the holder, which provides for adjusting the length of the electrode extension from the holder. Because of the high currents involved in the apparatus, any resistance caused by poor contact causes high temperatures to develop, and any imperfections in the contact between the holder and the electrode may result in arcing, which not only reduces the life of the electrode but generates substantial amounts of additional heat. For this reason it is highly important that a minimum of electrical resistance exist between the holder and the electrode, while at the same time providing means for easily moving the electrode relative to the holder.